Lithium secondary battery

Abstract

A lithium secondary battery including a positive electrode, a negative electrode comprising a negative electrode current collector, and an electrolyte interposed between the positive electrode and negative electrode. The lithium metal is formed on the negative electrode current collector by lithium ions migrating toward the negative electrode current collector after charge. The electrolyte comprises a sacrificial salt having an oxidation potential of 5 V or less with respect to lithium. The lithium secondary battery forms lithium metal while being blocked from the atmosphere, and thereby improves an existing problem caused by high reactivity of lithium metal. By including a sacrificial salt in an electrolyte, lithium consumption caused by an irreversible reaction of a negative electrode is reduced, which may prevent decline in the battery capacity and lifetime properties.

Description

TECHNICAL FIELD[0001]This application claims the benefit of Korean Patent Application No. 10-2018-0130620 on Oct. 30, 2018 and Korean Patent Application No. 10-2019-0136866 on Oct. 30, 2019 with the Korean Intellectual Property Office, the disclosure of which are herein incorporated by reference in their entirety.[0002]The present invention relates to a lithium secondary battery having a negative electrode free structure using an electrolyte including a sacrificial salt.BACKGROUND ART[0003]With the rapid development of electric, electronic, communications and computer industries, demands for high performance and high stability secondary batteries have rapidly increased recently. Particularly, with the trend of battery and electronic products being lighter, thinner, smaller and portable, weight lightening and miniaturization have been required for a second battery, a key component, as well. In addition, as the needs for a new type of energy supply has increased due to an environmenta...

AI Technical Summary

Benefits of technology

The present invention provides a lithium secondary battery that can be coated while being blocked from the atmosphere. This process prevents the formation of a surface oxide layer on the lithium metal due to oxygen and moisture in the atmosphere. This results in a longer battery life. The inclusion of a sacrificial salt in the electrolyte maximizes battery capacity and prevents an irreversible capacity loss during charging and discharging. Additionally, a long lifetime can be achieved.

Problems solved by technology

In addition, as the needs for a new type of energy supply has increased due to an environmental pollution problem and fossil exhaustion, necessity for developing an electric vehicle capable of resolving such a problem has increased.

At this time, capacity of the lithium secondary battery varies depending on the type of an electrode active material, and commercialization has not been achieved since sufficient capacity as theoretical capacity has not been secured during actual driving.

However, when using a metal such as silicon or tin as a negative electrode active material, the volume significantly expands to approximately 4 times during a charging process of alloying with lithium, and shrinks during discharge.

Due to such large changes in the volume of the electrode repeatedly occurring during charge and discharge, the active material is gradually micronized and deintercalated from the electrode resulting in a rapid decrease in the capacity, and as a result, commercialization has not been achieved since stability and reliability have not been secured.

And since lithium explosively reacts with water and readily reacts with oxygen in the atmosphere as an alkali metal having high reactivity, manufacturing and use are difficult under a general environment.

Such an oxide layer functions as an insulating film lowering electric conductivity and inhibiting lithium ion migration, and a problem of increasing internal resistance of a battery occurs.

Due to such high instability of lithium metal, lithium metal batteries using lithium metal as a negative electrode have not been commercialized.

Although the prior art document somewhat improved a problem of forming an oxide layer, which is due to lithium metal reactivity, by conducting a vacuum deposition process when forming a lithium negative electrode, fundamentally suppressing oxide layer formation has not yet been achieved since the electrode is still exposed to the atmosphere during a battery assembling process.

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